1. Field
Example embodiments relate to a method of manufacturing a vertical light emitting device including a passivation layer formed on a sidewall of the vertical light emitting device which may prevent current leakage.
2. Description of Related Art
Light emitting devices (e.g., light emitting diodes (LEDs)) are widely used for transmitting, recording, and/or reading data in communication devices (e.g., optical communication devices), for example, compact disc players (CDPs), digital versatile disc players (DVDPs), or similar. Light emitting devices are also widely applied to components for large-sized electronic sign boards and liquid crystal display devices, for example, backlights. Currently, LEDs formed of groups III-V compound semiconductors are mainly used. FIG. 1 is a cross-sectional view illustrating the general structure of a conventional vertical light emitting device.
Referring to FIG. 1, the conventional vertical light emitting device includes a p-type electrode 11, a p-type semiconductor layer 12, an active layer 13, and a n-type semiconductor layer 14 which are sequentially formed on a metal supporting layer 10. The n-type electrode 15 is electrically connected to a part of the surface of the n-type semiconductor layer 14.
If the conventional vertical light emitting device is a GaN based light emitting device, the p-type semiconductor layer 12 is composed of a p-GaN compound semiconductor, the n-type semiconductor layer 14 is formed of a n-GaN compound semiconductor, and the active layer 13 is formed of an InxGa1-xN compound semiconductor having a multi quantum well (MQW) structure. In addition, the p-type electrode 11 is formed of a metal (e.g., Ag, Au, Ni, Ru, or similar), and the n-type electrode 15 is formed of a metal (e.g., Ti/Al, or similar).
When a voltage is applied between the p-type electrode 11 and the n-type electrode 15, an electron is injected from the n-type electrode 15 to the n-type semiconductor layer 14, and a hole is injected from the p-type electrode 11 to the p-type semiconductor layer 12. When the electron and the hole are combined, light is emitted. The emitted light passes through the surface of the n-type semiconductor layer 14 and is radiated to the outside.
However, in a conventional vertical light emitting device having the above structure, current may leak through the sidewalls of the conventional vertical light emitting device. In order to prevent current leakage, a passivation layer formed of an insulating material is formed on the sidewalls of the conventional vertical light emitting device.
FIGS. 2A through 2G are cross-sectional views illustrating a method of manufacturing a conventional vertical light emitting device including a passivation layer.
Referring to FIG. 2A, emissive layers 30 are formed on a sapphire substrate 20. The emissive layers 30 are formed by sequentially forming a n-GaN semiconductor layer 31, an active layer 32, and a p-GaN semiconductor layer 33 on the sapphire substrate 20. Trenches 92 are then formed by etching the emissive layers 30. The trenches 92 each define the emissive layers 30 as a light emitting device unit. Because the trenches 92 are formed by etching the emissive layers 30 using the inductively coupled plasma-reactive ion etching (ICP-RIE) method, sides of the trenches 92 (e.g., sidewalls of the emissive layers 30) are formed to be inclined.
Referring to FIG. 2B, a p-type electrode 40 is formed on the p-GaN semiconductor 33 of the emissive layers 30. A post 94 is then formed by filling the inside of the trench 92 with a photoresist (PR).
Referring to FIG. 2C, a metal supporting layer 50 formed of Cu, Cr, or Ni is formed on the post 94 and the p-type electrode 40.
Referring to FIG. 2D, when the sapphire substrate 20 is separated and the post 94 is removed using a laser lift off (LLO) method, just the emissive layers 30 divided by the trenches 92 and the p-type electrodes 40 remain on the metal supporting layer 50.
Referring to FIG. 2E, a n-type electrode 60 is formed on the n-GaN semiconductor layer 31 of the emissive layers 30.
Referring to FIG. 2F, a passivation layer 70 is formed to protect the conventional vertical light emitting device and prevent current from leaking through the sidewalls of the conventional vertical light emitting device. The passivation layer 70 is formed by depositing an insulating material, for example, SiO2, in the trenches 92 formed between the emissive layers 30 using a plasma enhanced chemical vapor deposition (PECVD) method.
Referring to FIG. 2G, the resulting structure of FIG. 2F is divided into light emitting device units using a sawing method or a laser scribing method. A light emitting device which includes the passivation layer 70 formed on the sidewalls of the emissive layers 30 is thereby manufactured.
The conventional manufacturing method has certain recognized problems. First, when a laser beam is irradiated on the emissive layers 30 formed of GaN during the LLO method, GaN is decomposed into gallium and nitrogen gas. A momentary shock wave occurs at an interface between each of the emissive layers 30 and the sapphire substrate 20 by the pressure of the generated nitrogen gas. The shock wave is concentrated toward the post 94 formed of a PR, which is softer than the other elements. The shock wave occurring at the post 94 accelerates the division between the post 94 and each of the emissive layers 30. Thus, a crack occurs on the emissive layers 30 placed below the interface between the p-type electrode 40 and the post 94 and further spreads inside the emissive layers 30.
FIGS. 3A and 3B are images of cracks occurring in an emissive layer when the LLO method is performed when the conventional vertical light emitting device is manufactured.
Referring to FIGS. 3A and 3B, cracks occurring inside an emissive layer can be seen. A light emitting device having cracks in the emissive layer cannot normally be used.
Second, because the sidewalls of the emissive layers 30 are reversely inclined when the passivation layer 70 is formed in the trench 92 between the emissive layers 30 as described above, it is difficult to uniformly deposit the passivation layer 70. Typically, when the passivation layer 70 is deposited using a PECVD method at a temperature of 300° or more, heat is generated. Thus, a connection defect occurs at the interface between the emissive layer 30 and each of the p-type electrode 40 and the n-type electrode 60, which are already formed, due to the heat. Accordingly, the characteristics of the light emitting device may deteriorate.
Third, referring to FIG. 2G, the passivation layer 70 is cut together with the metal supporting layer 50 using a sawing or a laser scribing method. As such, if the passivation layer 70 is damaged, almost or part of the passivation layer 70 may be detached from the sidewalls of the emissive layers 30.